Yes, your cat needs a vet like you need to breathe. This is not an optional vet trip. Nobody is going to be able to tell you anything else to do than go directly to the vet, because that is what your cat needs. Not eating for days on end is potentially fatal and not going to the bathroom is too.
There are lots of things you can do to get the money, get creative. You can sell things you don't need anymore, borrow the money, use your credit card, etc. If you aren't regularly bringing her to a vet, you might have a hard time getting one to give you a payment plan, but call the shelters in the area like Abby'sMom suggested and they might be able to point you in the right direction.
Or you can try Care Credit:http://www.carecredit.com/providerloc/
click Veterinary and then type in your zip.
Also try contacting this org:http://www.imom.org/
Savannah, I understand it's hard when you're broke, but you absolutely must take her to the vet. This is one of the promises you make your cat when you adopt her. If you were in so much pain, you would find a way to get medical treatment, right? While it may not be as easy to just go to the vet, since you're broke, where there is a will there is a way, and we know you want to do what's best for her, so you'll figure out something. But you need to take her to the vet, honestly, you needed to take her days ago.
And consider buying pet insurance for the next time this comes up.